Methods for reception of csi-rs and csi feedback in nr-u

ABSTRACT

A method for use in a wireless transmit/receive unit is disclosed. The method may comprise: obtaining a transmission occasion for a channel state information reference signal (CSI-RS); obtaining at least one conditional transmission occasion for the CSI-RS; and determining whether the CSI-RS is transmitted in the transmission occasion, wherein on a condition that the CSI-RS is not transmitted in the transmission occasion, detecting if the CSI-RS is transmitted in one of the at least one conditional transmission occasion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/886,159, filed Aug. 13, 2019, the contents of which are incorporatedherein by reference.

BACKGROUND

Transmissions in New Radio Unlicensed spectrum (NR-U) are subject to thechannel having been acquired. Therefore, signals with fixedperiodicities may not be transmitted at every configured occasion.Examples of such signals include periodic or semi-persistent ChannelState Information Reference Signal (CSI-RS). Nevertheless, there arebenefits to configuring periodic or semi-persistent CSI-RS in NR-U. Forexample, the signaling overhead is reduced when compared to aperiodicCSI-RS. Maximum Channel Occupancy Time (COT) duration means that anyreduction in signaling, and thus reduction in channel acquisition, isbeneficial. Another benefit is that a WTRU (Wireless Transmit/ReceiveUnit) may be able to receive CSI-RS even outside of a formally definedCOT.

However, a problem may arise in that a WTRU must determine whether aCSI-RS was actually transmitted in an occasion or whether it was droppeddue to the channel having not been acquired. This is necessary giventhat it may impact the measurements that the WTRU may perform and maylead to incorrect assumptions on the channel characteristics. Suchincorrect measurements, assumptions and measurement feedback may lead toincorrect WTRU scheduling, which may greatly impact system throughput.Furthermore, incorrect measurements may lead to unnecessary feedbackreports which may also reduce overall system performance due tounnecessary channel acquisition.

SUMMARY

A method for use in a wireless transmit/receive unit is disclosed. Themethod may comprise: obtaining a transmission occasion for a channelstate information reference signal (CSI-RS); obtaining at least oneconditional transmission occasion for the CSI-RS; and determiningwhether the CSI-RS is transmitted in the transmission occasion, whereinon a condition that the CSI-RS is not transmitted in the transmissionoccasion, detecting if the CSI-RS is transmitted in one of the at leastone conditional transmission occasion.

A wireless transmit/receive unit (WTRU) is disclosed. The WTRU maycomprise: a processor, configured to obtain a transmission occasion fora channel state information reference signal (CSI-RS); obtain at leastone conditional transmission occasion for the CSI-RS; and determinewhether the CSI-RS is transmitted in the transmission occasion, whereinon a condition that the CSI-RS is not transmitted in the transmissionoccasion, the processor is further configured to detect if the CSI-RS istransmitted in one of the at least one conditional transmissionoccasion.

As discussed, in order to prevent incorrect measurements as well asincorrect measurement feedback, methods are needed to enable the WTRU todetermine whether a CSI-RS is present. Methods may also be needed toincrease the robustness of CSI-RS transmission considering the need forsuccessful channel acquisition prior to transmission. The WTRU may alsoneed methods to handle measurements and report appropriate valuesconsidering missing CSI-RS transmissions. Moreover, feedback resourcesmay also require an increase in robustness considering the channelacquisition requirement.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings,wherein like reference numerals in the figures indicate like elements,and wherein:

FIG. 1A is a system diagram illustrating an example communicationssystem in which one or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram illustrating an example wirelesstransmit/receive unit (WTRU) that may be used within the communicationssystem illustrated in FIG. 1A according to an embodiment;

FIG. 1C is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A according to an embodiment;

FIG. 1D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 1A according to an embodiment;

FIG. 2 is a diagram illustrating an indication of presence of ChannelState Information Reference Signal (CSI-RS) resources;

FIG. 3 is a diagram of a WTRU determining the presence or absence of aprevious CSI-RS based on a sequence of a currently received CSI-RS; and

FIG. 4A is a flowchart illustrating a method according to an embodimentof this application; and

FIG. 4B is a diagram of a CSI-RS configured every m^(th) slot.

DETAILED DESCRIPTION

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word discrete Fourier transform Spread OFDM (ZT-UW-DFT-S-OFDM),unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bankmulticarrier (FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network (CN) 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d, any of which maybe referred to as a station (STA), may be configured to transmit and/orreceive wireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watchor other wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a NodeB, an eNode B(eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as agNode B (gNB), a new radio (NR) NodeB, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, and the like. The base station 114 a and/or the base station 114b may be configured to transmit and/or receive wireless signals on oneor more carrier frequencies, which may be referred to as a cell (notshown). These frequencies may be in licensed spectrum, unlicensedspectrum, or a combination of licensed and unlicensed spectrum. A cellmay provide coverage for a wireless service to a specific geographicalarea that may be relatively fixed or that may change over time. The cellmay further be divided into cell sectors. For example, the cellassociated with the base station 114 a may be divided into threesectors. Thus, in one embodiment, the base station 114 a may includethree transceivers, i.e., one for each sector of the cell. In anembodiment, the base station 114 a may employ multiple-input multipleoutput (MIMO) technology and may utilize multiple transceivers for eachsector of the cell. For example, beamforming may be used to transmitand/or receive signals in desired spatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink(DL) Packet Access (HSDPA) and/or High-Speed Uplink (UL) Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using NR.

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., an eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b may have a direct connection tothe Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106.

The RAN 104 may be in communication with the CN 106, which may be anytype of network configured to provide voice, data, applications, and/orvoice over internet protocol (VoIP) services to one or more of the WTRUs102 a, 102 b, 102 c, 102 d. The data may have varying quality of service(QoS) requirements, such as differing throughput requirements, latencyrequirements, error tolerance requirements, reliability requirements,data throughput requirements, mobility requirements, and the like. TheCN 106 may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the CN 106 may be in direct or indirectcommunication with other RANs that employ the same RAT as the RAN 104 ora different RAT. For example, in addition to being connected to the RAN104, which may be utilizing a NR radio technology, the CN 106 may alsobe in communication with another RAN (not shown) employing a GSM, UMTS,CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106 may also serve as a gateway for the WTRUs 102 a, 102 b, 102c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), anyother type of integrated circuit (IC), a state machine, and the like.The processor 118 may perform signal coding, data processing, powercontrol, input/output processing, and/or any other functionality thatenables the WTRU 102 to operate in a wireless environment. The processor118 may be coupled to the transceiver 120, which may be coupled to thetransmit/receive element 122. While FIG. 1B depicts the processor 118and the transceiver 120 as separate components, it will be appreciatedthat the processor 118 and the transceiver 120 may be integratedtogether in an electronic package or chip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors. The sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor, an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, ahumidity sensor and the like.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) and DL(e.g., for reception) may be concurrent and/or simultaneous. The fullduplex radio may include an interference management unit to reduce andor substantially eliminate self-interference via either hardware (e.g.,a choke) or signal processing via a processor (e.g., a separateprocessor (not shown) or via processor 118). In an embodiment, the WTRU102 may include a half-duplex radio for which transmission and receptionof some or all of the signals (e.g., associated with particularsubframes for either the UL (e.g., for transmission) or the DL (e.g.,for reception)).

FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 1C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (PGW) 166. While the foregoing elements are depicted as part ofthe CN 106, it will be appreciated that any of these elements may beowned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have access or an interface to a Distribution System(DS) or another type of wired/wireless network that carries traffic into and/or out of the BSS. Traffic to STAs that originates from outsidethe BSS may arrive through the AP and may be delivered to the STAs.Traffic originating from STAs to destinations outside the BSS may besent to the AP to be delivered to respective destinations. Trafficbetween STAs within the BSS may be sent through the AP, for example,where the source STA may send traffic to the AP and the AP may deliverthe traffic to the destination STA. The traffic between STAs within aBSS may be considered and/or referred to as peer-to-peer traffic. Thepeer-to-peer traffic may be sent between (e.g., directly between) thesource and destination STAs with a direct link setup (DLS). In certainrepresentative embodiments, the DLS may use an 802.11e DLS or an 802.11ztunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may nothave an AP, and the STAs (e.g., all of the STAs) within or using theIBSS may communicate directly with each other. The IBSS mode ofcommunication may sometimes be referred to herein as an “ad-hoc” mode ofcommunication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width. The primarychannel may be the operating channel of the BSS and may be used by theSTAs to establish a connection with the AP. In certain representativeembodiments, Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA) may be implemented, for example in 802.11 systems. ForCSMA/CA, the STAs (e.g., every STA), including the AP, may sense theprimary channel. If the primary channel is sensed/detected and/ordetermined to be busy by a particular STA, the particular STA may backoff. One STA (e.g., only one station) may transmit at any given time ina given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications (MTC), such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode) transmitting to the AP, all available frequency bands may beconsidered busy even though a majority of the available frequency bandsremains idle.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 1D is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 104 may also be in communication with theCN 106.

The RAN 104 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 104 may include any number of gNBs whileremaining consistent with an embodiment. The gNBs 180 a, 180 b, 180 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the gNBs 180 a, 180 b, 180 c may implement M IMO technology. Forexample, gNBs 180 a, 108 b may utilize beamforming to transmit signalsto and/or receive signals from the gNBs 180 a, 180 b, 180 c. Thus, thegNB 180 a, for example, may use multiple antennas to transmit wirelesssignals to, and/or receive wireless signals from, the WTRU 102 a. In anembodiment, the gNBs 180 a, 180 b, 180 c may implement carrieraggregation technology. For example, the gNB 180 a may transmit multiplecomponent carriers to the WTRU 102 a (not shown). A subset of thesecomponent carriers may be on unlicensed spectrum while the remainingcomponent carriers may be on licensed spectrum. In an embodiment, thegNBs 180 a, 180 b, 180 c may implement Coordinated Multi-Point (CoMP)technology. For example, WTRU 102 a may receive coordinatedtransmissions from gNB 180 a and gNB 180 b (and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containing avarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, DC, interworking between NR andE-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184 b, routing of control plane information towards Access andMobility Management Function (AMF) 182 a, 182 b and the like. As shownin FIG. 1D, the gNBs 180 a, 180 b, 180 c may communicate with oneanother over an Xn interface.

The CN 106 shown in FIG. 1D may include at least one AMF 182 a, 182 b,at least one UPF 184 a,184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whilethe foregoing elements are depicted as part of the CN 106, it will beappreciated that any of these elements may be owned and/or operated byan entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 104 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different protocol data unit (PDU)sessions with different requirements), selecting a particular SMF 183 a,183 b, management of the registration area, termination of non-accessstratum (NAS) signaling, mobility management, and the like. Networkslicing may be used by the AMF 182 a, 182 b in order to customize CNsupport for WTRUs 102 a, 102 b, 102 c based on the types of servicesbeing utilized WTRUs 102 a, 102 b, 102 c. For example, different networkslices may be established for different use cases such as servicesrelying on ultra-reliable low latency (URLLC) access, services relyingon enhanced massive mobile broadband (eMBB) access, services for MTCaccess, and the like. The AMF 182 a, 182 b may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro,and/or non-3GPP access technologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN106 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 106 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating UE IP address,managing PDU sessions, controlling policy enforcement and QoS, providingDL data notifications, and the like. A PDU session type may be IP-based,non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 104 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering DL packets, providing mobility anchoring, and the like.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 106 and the PSTN 108. In addition, the CN 106may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneembodiment, the WTRUs 102 a, 102 b, 102 c may be connected to a local DN185 a, 185 b through the UPF 184 a, 184 b via the N3 interface to theUPF 184 a, 184 b and an N6 interface between the UPF 184 a, 184 b andthe DN 185 a, 185 b.

In view of FIGS. 1A-1D, and the corresponding description of FIGS.1A-1D, one or more, or all, of the functions described herein withregard to one or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B160 a-c, MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184a-b, SMF 183 a-b, DN 185 a-b, and/or any other device(s) describedherein, may be performed by one or more emulation devices (not shown).The emulation devices may be one or more devices configured to emulateone or more, or all, of the functions described herein. For example, theemulation devices may be used to test other devices and/or to simulatenetwork and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

Operation in an unlicensed frequency band may be subject to some limitson the Transmit Power Control (TPC), the Radio Front end (RF) outputpower, and power density given by the mean Effective Isotropic RadiatedPower (EIRP) and the mean EIRP density at the highest power level. Itmay further be subject to requirements on the transmitter out of bandemissions. The foregoing may be specific to bands and/or geographicallocations.

Operation may be further subject to requirements on the Nominal ChannelBandwidth (NCB) and the Occupied Channel Bandwidth (OCB) defined forunlicensed spectrum in the 5 GHz region. The NCB, i.e., the widest bandof frequencies inclusive of guard bands assigned to a single channel,may be at least 5 MHz at all times. The OCB, i.e., the bandwidthcontaining 99% of the power of the signal, may be between 80% and 100%of the declared NCB. During an established communication, a device maybe allowed to operate temporarily in a mode where its OCB may be reducedto as low as 40% of its NCB with a minimum of 4 MHz.

Channel access in an unlicensed frequency band may typically use aListen-Before-Talk (LBT) mechanism. LBT may be typically mandatedindependently of whether the channel is occupied or not.

For frame-based systems, LBT may be characterized by one or more of thefollowing items: a Clear Channel Assessment (CCA) time (e.g., 20 μs), aChannel Occupancy time (e.g., minimum 1 ms, maximum 10 ms), an idleperiod (e.g., minimum 5% of the channel occupancy time), a fixed frameperiod (e.g., equal to the channel occupancy time+the idle period), ashort control signaling transmission time (e.g., maximum duty cycle of5% within an observation period of 50 ms), a CAA energy detectionthreshold, etc. Typically, a 50 ms observation period may be dividedinto multiple duty cycles (e.g., 5%, 10%, 20%, 40%, 60%, etc.). Here x %represents the percentage of time where the LTE network is transmittingsignal.

For load-based systems (e.g., transmit/receive structure may not befixed in time), LBT may be characterized by a number N corresponding tothe number of clear idle slots in extended CCA instead of the fixed timeperiod. N may be selected randomly within a range.

Deployment scenarios may include different standalone NR-basedoperation, different variants of dual connectivity operation, e.g.,E-UTRAN New Radio—Dual Connectivity (EN-DC) with at least one carrieroperating according to the LTE Radio Access Technology (RAT) or NR DCwith at least two sets of one or more carriers operating according tothe NR RAT, and/or different variants of Carrier Aggregation (CA), e.g.,possibly also including different combinations of zero or more carriersof each of LTE and NR RATs.

For example, for LTE, the following functionalities have been consideredfor a License Assisted Access (LAA) system: LBT before clear channelassessment discontinuous transmission on a carrier with limited maximumtransmission duration, carrier selection, Transmit Power Control (TPC),Radio Resource Management (RRM) measurements including cellidentification, and Channel-State Information (CSI) measurement,including channel and interference. The above-mentioned functionalitieswill be described in detail below.

The LBT procedure may be defined as a mechanism by which an equipmentmay apply a CAA check before using the channel. The CCA may at leastutilize energy detection to determine the presence or absence of othersignals on a channel in order to determine if this channel is occupiedor clear, respectively. European and Japanese regulations mandate theusage of LBT in the unlicensed bands. Apart from regulatoryrequirements, carrier sensing via LBT may be one way for fair sharing ofthe unlicensed spectrum and hence it is considered to be a vital featurefor fair and friendly operation in the unlicensed spectrum in a singleglobal solution framework.

In unlicensed spectrum, channel availability may not always beguaranteed. In addition, certain regions such as Europe and Japanprohibit continuous transmission and impose limits on the maximumduration of a transmission burse in the unlicensed spectrum. Therefore,discontinuous transmission with limited maximum transmission durationmay be a required functionality for LAA.

As there is a large available bandwidth of unlicensed spectrum, carrierselection may be required for LAA nodes to select the carriers with lowinterference and with that to achieve good coexistence with otherunlicensed spectrum deployments.

TPC is a regulatory requirement in some regions by which a transmittingdevice may be able to reduce its transmit power in proposed of 3 dB or 6dB compared to its maximum nominal transmit power. This requirement maynot need new specifications.

RRM measurements including cell identification may enable mobilitybetween SCells and robust operation in the unlicensed band.

A WTRU operating in an unlicensed carrier may also support the necessaryfrequency/time estimation and synchronization to enable RRM measurementsand successful reception of information on the unlicensed band.

3GPP has started a work item to support NR operation in unlicensed band.One of the objectives is to specify NR-based operation in unlicensedspectrum, including initial access, scheduling/Hybrid Automatic RepeatRequest (HARQ), and mobility, along with coexistence methods withLTE-LAA and other incumbent RATs. Deployment scenarios may includedifferent standalone NR-based operations, different variants of dualconnectivity operation, e.g., EN-DC with at least one carrier operatingaccording to the LTE RAT or NR DC with at least two sets of one or morecarriers operating according to the NR RAT, and/or different variants ofCarrier Aggregation (CA), possibility also including differentcombinations of zero or more carriers of each of LTE and NR RATs.

New Radio unlicensed (NR-U) may support four categories of channelaccess schemes for NR-U operations. Category 1 may comprise immediatetransmission after a short switching gap. Category 2 may comprise LBTwithout random back-off. Category 3 may comprise LBT with randomback-off with fixed contention widow size. Category 4 may comprise LBTwith random back-off with variable contention widow size.

LBT has also been agreed to be performed using clear channel assessmentson so-called LBT subbands of 20 MHz. A Bandwidth Part (BWP) may be asingle LBT subband or may be composed of multiple LBT subbands.

The time during which a channel has been acquired for transmission maybe deemed as a Channel Occupancy Time (COT). The COT may be acquired bya WTRU or by a base station and may be subsequently shared with theother node. The total COT duration, including any sharing, may notexceed maximum COT.

Different embodiments according to the present application will bedescribed below. In this application, different solutions are disclosedfor a WTRU to operate with incomplete CSI-RS given that channelacquisition failure may affect the presence of some CSI-RStransmissions. The solutions disclosed herein may be applicable to anytype of RS (not just CSI-RS) and may be applicable to any signalexpected by the WTRU, which may not be present due to failure to acquirethe channel to transmit by the gNB.

The first embodiment will be described below. In the first embodiment,for the purpose of determining whether a CSI-RS has been transmitted ornot, a WTRU may determine presence of a CSI-RS resource. That is, theWTRU may be configured with a CSI-RS resource on which either a periodicor semi-persistent CSI-RS is expected, and the WTRU may determine theactual presence of the CSI-RS resource prior to performing measurementsor prior to feeding back such measurements in order to determine whethera CSI-RS has been transmitted or not. In this embodiment, the WTRU maydetermine presence of a CSI-RS through one or more of the followingitems: (1) explicit indication of presence of a CSI-RS resource, (2)implicit indication of presence of a CSI-RS resource, (3) determinationof CSI-RS presence based on WTRU measurement, and (4) determination ofCSI-RS presence based on a condition being met. The above-mentioneditems as well as different solutions related to those items will bedescribed below with reference to detailed embodiments.

A solution related to the explicit indication of presence of a CSI-RSresource will be described below. In order to determine if a CSI-RS hasbeen transmitted, the WTRU may receive an indication from the network.For example, the WTRU may receive an indication from the gNB providingan explicit list of CSI-RS resources that have been transmitted. Such anindication may represent all CSI-RS resources expected within a certaintime period prior to the indication being received by the WTRU. Theindication may be a bitmap of all expected CSI-RS or a toggled bitindicating the CSI-RS resource transmitted. In another example, theindication may provide a list of CSI-RS index values and/or a list ofoccasions where the CSI-RS has been actually transmitted. In thisapplication, unless otherwise indicated, the terms “CSI-RS” and “CSI-RSresource” may be used interchangeably. It will be appreciated that sincethe indication is provided from the network and thus it is explicit tothe WTRU (i.e., the WTRU does not necessarily do too much to process theindication in order to obtain the information it needs), this indicationmay be considered to be an “explicit” indication as opposed to the“implicit” indication discussed below.

In another example, the indication may provide a list of time resources(e.g., slots) where the based station (i.e., gNB) performedtransmissions. The WTRU may use this indication as a mask over allpossible CSI-RS transmissions and determine that CSI-RS was only evertransmitted in slots that the base station performed transmissions. Suchan indication may be used as a post hoc slot blanking pattern. The WTRUmay use the slot banking pattern to better determine the slots whereCSI-RS has been transmitted or where an interference may be measured.This may enable the WTRU to report two steps of interferencemeasurements: an interference measurement during an active COT and aninterference measurement out of COT. Such values may help to determinethe presence of hidden nodes and also the probability of acquiring thechannel.

The above-discussed indication will be further described with referenceto FIG. 2. FIG. 2 is a diagram illustrating an indication of presence ofCSI-RS resources. As shown in FIG. 2. a WTRU may be configured withCSI-RS and Channel State Information Interference Measurement (CSI-IM)every m slots. The WTRU may then receive an indication (e.g., in slot2m+3) of the previous slots where CSI-RS was indeed transmitted by thenetwork. Based on the indication, the WTRU may determine the appropriatereference slot for an upcoming CSI feedback report. Furthermore, theWTRU may segregate the CSI-IM into two groups, those occurring when itsserving cell had acquired the unlicensed channel (e.g., in slots 0 andm) and those occurring when the serving cell had not acquired thechannel (e.g., in slot 2m). The WTRU may obtain different reports (e.g.,different interference measurement reports) based on those two types ofCSI-IM and may feedback multiple values.

In embodiments, the indication of the actual transmission of CSI-RS maybe received by the WTRU in a periodic CSI request. Such a request maypoint to a specific transmission occasion of a CSI-RS resource and theWTRU may assume that any transmission occasion of a CSI-RS resourceindicated in a periodic CSI request was actually transmitted by the gNB.

A solution related to the implicit indication of presence of a CSI-RSresource will be described below. In embodiments, the implicitindication may be a parameter of a subsequent CSI-RS transmission. Thatis, the WTRU may determine the presence of a previous CSI-RS based on aparameter of a subsequent CSI-RS transmission, e.g., a subsequentCSI-RS. For example, a parameter of a CSI-RS may cycle through someconfigured values at each successful transmission. The WTRU may attemptto blindly decode a current CSI-RS using the different possibleparameters. Upon detecting the appropriate parameter used for thecurrent transmission (e.g., the current CSI-RS), the WTRU may determinewhether previous CSI-RS resources have been actually transmitted or not.The CSI-RS parameters that may be cycled may include at least one of:sequence, CSI-RS resource mapping, antenna ports, orthogonal cover code,and the like.

In embodiments, the implicit indication may be a sequence of consecutiveCSI-RS resources, that is, the WTRU may be configured with CSI-RSresources with four possible seeds to generate the sequence. The seedsmay be cycled over each four transmissions. The WTRU may be able todetermine if up to three consecutive CSI-RS resources have not beentransmitted (e.g., due to failed channel acquisition).

The above-discussed implicit indication will be further described withreference to FIG. 3. FIG. 3 shows a WTRU determining the presence orabsence of a previous CSI-RS based on a sequence of a currently receivedCSI-RS. As shown in FIG. 3, at 301, the WTRU receives a CSI-RS in everyconfigured occasion and the WTRU performs detection by cycling through 4sequences. At 302, the WTRU does not detect a CSI-RS in slot m or slot2m. The WTRU may then receive a CSI-RS in slot 3m with sequence 2. Thismay indicate to the WTRU that there was indeed no CSI-RS transmitted inslots m and 2m. This may also be used by the WTRU to determine thereference slot for a future CSI feedback report. At 303, the WTRU doesnot detect a CSI-RS in slot m or slot 2m. The WTRU may then receive aCSI-RS in slot 3m with sequence 3. This may indicate to the WTRU that itmissed a transmitted CSI-RS (i.e., a CSI-RS that used sequence 2) ineither slot m or slot 2m. It should be appreciated that the aboveexample with 4 sequences for CSI-RS transmission shown in FIG. 3 is notintended to be exclusive or be limiting to the present application. Anyother sequences may be available as long as they may help to realize theprinciple of this application.

In embodiments, the WTRU may not be able to determine which slot had anundetected CSI-RS and may not be able to use that information todetermine appropriate measurements based on the previously assumednon-transmitted CSI-RS. In other embodiments, a parameter of the CSI-RSmay be modified to enable the WTRU to determine a specific slot wherethe CSI-RS was missing. For example, the sequence of a subsequent CSI-RSmay be determined based on whether one or more previous CSI-RS wasskipped and the slot where it was skipped.

A solution related to the determination of CSI-RS presence based on WTRUmeasurement will be described below. The WTRU may determine that aCSI-RS is present based on a measurement taken on a resource where theWTRU expects the CSI-RS. For example, the WTRU may performsignal-to-interference-plus-noise ratio (SINR) measurements, and anyvalue below a threshold may lead to the WTRU's assumption that theCSI-RS was not transmitted on the resource. The threshold may beconfigurable.

In another embodiment, the WTRU may perform channel acquisitionmeasurements (e.g., clear channel assessment) prior to a transmission ofan expected CSI-RS resource. The WTRU may determine whether the channelis busy prior to the CSI-RS transmission. If the WTRU determines thechannel is busy immediately preceding the transmission of the expectedCSI-RS resource, it may assume the CSI-RS resource is not transmitted inthat instance. Typically, the above-discussed determination may beperformed by a processor in the WTRU. Here in this application, unlessotherwise indicated, a process performed by the WTRU may typically beperformed by its processor.

The WTRU may assume that a CSI-RS resource is present only if acondition is met. In embodiments, if a transmission occasion of a CSI-RSresource coincides with at least one of other transmissions from the gNBand that one of other transmissions is present, then the WTRU may assumethat the CSI-RS resource was also transmitted. For example, the WTRU maybe configured with a signal, such as a demodulation reference signal(DMRS), to be transmitted in conjunction with a CSI-RS. If the WTRUsuccessfully detects the associated DMRS, the WTRU may assume that theCSI-RS was also transmitted.

In embodiments, the WTRU may only assume a CSI-RS is present if it istransmitted on resources of an active COT. For example, a CSI-RSoccasion occurring on LBT subbands of an active COT may be assumedpresent by the WTRU. Therefore, the WTRU may determine the presence ofthe CSI-RS resource based on an indication of the COT structure,possibly received prior to the transmission occasion of the CSI-RS.

The second embodiment will be described below. The second embodiment isdirected to increase the robustness of CSI-RS transmission under acircumstance where a CSI-RS is missing due to a failure of channelacquisition. Increasing the robustness of CSI-RS transmission may berealized by increasing the probability that a periodic orsemi-persistent CSI-RS is transmitted. In order to improve theprobability that the CSI-RS is transmitted, a WTRU may be configuredwith multiple transmission occasions tied to a single CSI-RStransmission. In such a case, the WTRU may not expect a single CSI-RStransmission to be transmitted on more than one occasion. Therefore, inthe second embodiment, upon determining that a CSI-RS resource hasindeed been transmitted in a transmission occasion, the WTRU may notneed to continue monitoring other occasions (i.e., conditionaloccasions) tied to that CSI-RS transmission, and upon determining thatthe CSI-RS resource has not been transmitted in the transmissionoccasion, the WTRU may need to continue monitoring other occasions tiedto that CSI-RS transmission.

The second embodiment will be described in detail below with referenceto FIGS. 4A-4B. FIG. 4A is a flowchart illustrating method 400 accordingto the second embodiment. As shown in FIG. 4A, method 400 may comprise:at 401, obtaining a transmission occasion for a CSI-RS; at 402,obtaining at least one conditional transmission occasion for the CSI-RS;and at 403, determining whether the CSI-RS is transmitted in thetransmission occasion, wherein on a condition that the CSI-RS is nottransmitted in the transmission occasion, at 404, detecting if theCSI-RS is transmitted in one of the at least one conditionaltransmission occasion. The above-mentioned processes 401-404 will bedescribed below with reference to detailed examples.

Accordingly, the WTRU may comprise a processor. The processor isconfigured to obtain a transmission occasion for a channel stateinformation reference signal (CSI-RS); to obtain at least oneconditional transmission occasion for the CSI-RS; and to determinewhether the CSI-RS is transmitted in the transmission occasion. On acondition that the CSI-RS is not transmitted in the transmissionoccasion, the processor is further configured to detect if the CSI-RS istransmitted in one of the at least one conditional transmissionoccasion.

As shown in FIG. 4A, at 401, the method 400 may comprise obtaining atransmission occasion for a CSI-RS.

The transmission occasion may be obtained without any furtherprocessing. In embodiments, the transmission occasion may be pre-storedin a memory of the WTRU, and the WTRU may retrieve the transmissionoccasion from the memory. In embodiments, the transmission occasion maybe obtained from the network. In embodiments, the transmission occasionmay be obtained from the base station or a 3rd-party device other thanthe base station. It will be appreciated that the above embodimentsregarding different sources of the transmission occasion are notintended to be exclusive or be limiting to the present application.

The transmission occasion may be obtained through additional processing.In embodiments, the transmission occasion may be obtained by processingone or more parameters. The parameters may comprise a reference slot ora default slot, a timing offset, a periodicity, etc. To process at leastone of the parameters may obtain the transmission occasion.

For example, at 401, the process of determining the transmissionoccasion for the CSI-RS may further comprise: obtaining a transmissionoccasion configuration comprising a timing offset and a periodicity; anddetermining, based on the timing offset and the periodicity, a timing ofthe transmission occasion. Accordingly, the WTRU may be configured toobtain a CSI-RS transmission occasion configuration that comprises atiming offset and a periodicity, and to determine, based on the timingoffset and the periodicity, a timing of the transmission occasion. Inother words, such offset and periodicity may enable the WTRU todetermine the timing of each CSI-RS resource occasion for that CSI-RSconfiguration.

The transmission occasion configuration may be obtained in the same orsimilar fashion as the above-discussed transmission occasion. Forexample, the transmission occasion configuration may be obtained fromthe network, the base station, a 3rd-party device or the memory of theWTRU. This application also does not limit the source of theconfiguration as long as the configuration may help to realize theprinciple of this application.

The timing offset and the periodicity in the transmission occasionconfiguration may be used to determine the timing of the transmissionoccasion. The timing offset may represent a timing offset value withrespect to a reference timing (e.g., a reference slot). The periodicitymay represent the length between two successive transmission occasions,that is, how many slots within a transmission occasion periodicity. Forexample, the value of the timing offset is 0, and the value of theperiodicity is m. In that case, the WTRU may determine that thetransmission occasion is slot 0, slot m, slot 2m, etc. Thus the timingof the transmission occasion may be obtained. It will be appreciatedthat the above-discussed timing offset and the periodicity as well astheir values are given as an example, and they are not intended to beexclusive or be limiting to the present application. The above-discussedprocess at 401 will be further described later below with reference toFIG. 4B.

As shown in FIG. 4, method 400 may comprise: at 402, obtaining at leastone conditional transmission occasion for the CSI-RS. That is, the WTRUmay obtain one or more conditional transmission occasions associated tothe CSI-RS transmission occasion obtained at 401.

The at least one conditional transmission occasion may be obtainedwithout any further processing. The at least one conditionaltransmission occasion may be obtained in the same or similar fashion asthe above-discussed transmission occasion. For example, the at least oneconditional transmission occasion may be obtained from the network, thebase station, a 3rd-party device or the memory of the WTRU. Thisapplication also does not limit the source of the conditionaltransmission occasion as long as it may help to realize the principle ofthis application.

The at least one conditional transmission occasion may be obtainedthrough additional processing. In embodiments, the at least oneconditional transmission occasion may be obtained by processing one ormore parameters. The parameters may comprise a reference slot or adefault slot, a timing offset, a periodicity, etc. To process at leastone of the parameters may obtain the transmission occasion.

For example, at 402, the process of obtaining at least one conditionaltransmission occasion for the CSI-RS further may further comprise:obtaining a conditional transmission occasion configuration whichcomprises at least one conditional timing value; and determining, basedon the at least one conditional timing value, the at least oneconditional transmission occasion. Accordingly, to obtain at least oneconditional transmission occasion for the CSI-RS, the processor isfurther configured to obtain a conditional transmission occasionconfiguration which comprises at least one conditional timing value, andto determine, based on the at least one conditional timing value, the atleast one conditional transmission occasion.

The conditional transmission occasion configuration may indicate one ormore conditional timing values associated to the CSI-RS transmissionoccasion obtained at 401. Such conditional timing values may provideresources for one or more conditional CSI-RS transmissions, e.g., the atleast one conditional transmission occasion. For example, there is aconditional timing value, i.e., 5 in the conditional transmissionoccasion configuration, which represents that a conditional transmissionoccasion is the 5th slot after the transmission occasion obtained at401. For example, there are two conditional timing values, i.e., 5 and9, in the conditional transmission occasion configuration. In that case,there are two conditional transmission occasions, the 5th slot and the9th slot after the transmission occasion obtained at 401. It should beappreciated that the above examples regarding the conditional timingvalue are only given by way of example, and they are not intended to beexclusive or be limiting to the present application. The conditionaltransmission occasion will be further described later below withreference to FIG. 4B.

In embodiments, the conditional transmission occasion configuration andthe above-discussed transmission occasion configuration may beincorporated into a single configuration. That is to say, the WTRU mayobtain a single configuration which comprises both transmission occasionconfiguration needed for the process at 401 and the conditionaltransmission occasion configuration needed for the process at 402.Therefore, the above-discussed parameters, such as the timing offset,the periodicity, and the conditional timing value, may be included intothis single configuration.

The conditional transmission occasion is used for the transmission of aCSI-RS and it is directed to a condition that a previous associatedtiming (e.g., a transmission occasion obtained at 401, a previousconditional transmission occasion obtained 402) was not used for theCSI-RS transmission. In this application, unless otherwise indicated,the terms “transmission occasion”, “CSI-RS transmission occasion”,“CSI-RS transmission” and “CSI-RS occasion” may be used interchangeably,while the terms “conditional transmission occasion”, “CSI-RS conditionaltransmission occasion”, “CSI-RS conditional transmission” and “CSIconditional occasion” may be used interchangeably.

As shown in FIG. 4A, after the process at 401, the WTRU may determinethat the timing offset is 0 and the periodicity is m, and may furtherdetermine that a CSI-RS transmission occasion is configured every m^(th)slot, the first CSI-RS transmission occasion is slot 0, and the nextCSI-RS transmission occasion is slot m. Furthermore, after the processat 402, the WTRU may determine that each CSI-RS transmission occasion isconfigured with two conditional timing values, i.e., 5 and 9. Therefore,the WTRU may determine that. the corresponding conditional transmissionoccasions with respect to slot 0 are slot 5 and slot 9, and thecorresponding conditional transmission occasions with respect to slot mare slot m+5 and slot m+9.

Then, the method 400 may proceed to the process at 403. At 403, themethod 400 may comprise determining whether the CSI-RS is transmitted inthe transmission occasion, wherein on a condition that the CSI-RS is nottransmitted in the transmission occasion, at 404, detecting if theCSI-RS is transmitted in one of the at least one conditionaltransmission occasion. The method 400 may further comprise on acondition that the CSI-RS is transmitted in the transmission occasion(i.e., “Yes” at 403), at 405, not detecting if the CSI-RS is transmittedin one of the at least one conditional transmission occasion.

The WTRU may only need to attempt a CSI-RS in a conditional transmissionoccasion if the CSI-RS was not transmitted in (1) the associated fixedtransmission occasion and (2) any previous conditional transmissionoccasions associated with the same fixed transmission occasion. Forexample, if the WTRU does not detect a CSI-RS in slot 0, then itmonitors slot 5 for the CSI-RS. Once it detects a CSI-RS in slot 5, itmay not need to monitor slot 9 for a CSI-RS transmission. In slot m, ifthe WTRU detects a CSI-RS, then it may not need to monitor anyassociated conditional transmission occasions in slot m+5 and slot m+9.If the WTRU detects a CSI-RS in a slot, the WTRU may assume resourcesmapped to subsequent conditional CSI-RS (for example, associated withthe detected CSI-RS resource) may be reused for the transmission ofother signals or channels. For example, the RE mapping of a transmissionoverlapping a transmitted conditional CSI-RS may require puncturing (orrate matching around) the resources of the conditional CSI-RS. The REmapping of a transmission overlapping the resources of an un-transmittedconditional CSI-RS may not require puncturing (or rate matching around)the resources of the conditional CSI-RS.

In the second embodiment, the WTRU may detect a CSI-RS in thetransmission occasion and the conditional transmission occasion throughthe methods disclosed in the above first embodiment. For example, theWTRU may determine whether a CSI-RS is transmitted based on anindication of presence of the CSI-RS resource. For another example, theWTRU may determine whether a CSI-RS is transmitted by detecting whethera channel is busy immediately preceding the transmission occasion. Thedifferent methods for detecting the CSI-RS transmission may be referredto the above first embodiment.

In the example illustrated in FIG. 4, the slot 0 is used as a referenceslot, and thus if the timing offset is 0, then the reference slot willbe used as transmission occasion for the CSI-RS. It will be appreciatedthat the reference slot may be any other available slot. Also, whenconfigured with a CSI-RS conditional timing value, a WTRU may use, as areference slot for a feedback measurement, any CSI-RS occasion or anyCSI-RS conditional occasion associated to the original reference slottied to the feedback measurement.

In embodiments, the WTRU may perform measurements on a CSI-RStransmission occasion and depending on if the measurement meets acriterion (e.g., a threshold value), the WTRU may determine whether toattempt detection of the CSI-RS in an upcoming associated conditionaltransmission occasion. Given that the WTRU may autonomously determinewhich resource to use to feedback CSI measurements, the WTRU mayindicate to the network which resource (original occasion or conditionaloccasion) it is using when providing feedback measurements. This mayenable the network to determine whether the WTRU is affected by a hiddenmode.

In embodiments, the WTRU may be configured with a CSI-RS resource whosetransmission occasion timing may depend on another transmission. Thatis, the transmission occasion obtained at 401 may be determined based onanother transmission. For example, the WTRU may expect the CSI-RStransmission occasion to be determined based on the timing of anassociated DMRS transmission or an associated DRS (discovery referencesignals) transmission. Given that a DMRS transmission or a DRStransmission may be transmitted at any moment during a pre-configuredwindow, the timing of associated CSI-RS may vary depending on the actualtime of the DMRS transmission or the DRS transmission. It should beappreciated that the above-discussed DMRS transmission and DRStransmission are only given by way of example, and they are not intendedto be exclusive or be limiting to the present application. Thetransmission occasion obtained at 401 may also depend on any otheravailable transmission as long as it may help to realize the principleof this application.

In embodiments, the WTRU may be configured with a CSI-RS resource forwhich at least one transmission parameter(s) (e.g. timing, bandwidth,sequence and the like) may depend on at least one parameter. That is,the CSI-RS transmission (for example, CSI-RS timing, CSI-RS frequency,the number of ports of a CSI-RS transmission during COT, a per-resourceblock structure of a CSI-RS, etc.) may be determined based on at leastone other parameter. The at least one other parameter may comprise a COTtiming (for example, a start timing of COT), a density of CSI-RStransmissions, etc. The following will describe the at least one otherparameter which may be used to determine a CSI-RS transmission occasionwith reference to detailed examples.

For example, the CSI-RS transmission occasion may be determined based ona start timing of the COT. In such an example, a CSI-RS resourceassociated to the CSI-RS transmission occasion may be configured with anoffset based on the starting timing of the COT. The CSI-RS resource mayalso be configured with a periodicity based on a duration of the COT.Since the start timing of the COT may vary, the CSI-RS transmissionoccasion may also vary. In this application, unless otherwise indicated,the start timing of a COT may also be referred to as a COT timing.

In some cases, such variable timing may lead to collision of the CSI-RStransmission with other transmissions. For example, a variable timingCSI-RS may collide with a non-variable timing CSI-RS, a DRS, a controlresource set (CORESET), or a DMRS. In such a case, the WTRU may use apossibly configurable priority of transmissions to determine where toexpect the presence of a CSI-RS at a given time. For example, a CSI-RSresource may have an index, and upon a collision occurring, the WTRU mayonly expect the presence of the CSI-RS with highest or lowest indexvalue.

The WTRU may expect all types of CSI-RS to use variable timing. Forexample, zero power (ZP) CSI-RS, used for physical downlink sharedchannel (PDSCH) mapping, may also be shifted according to a COT timingand/or duration.

The WTRU may be configured with an association of a report configurationwith one or several resource sets indicating a set of downlink resourceson which measurement of CSI should be carried out. However, due to theuncertainty of LBT and the start timing of the COT, the network may notshift or switch the CSI-RS transmission to further timesymbol/slots/frame and/or adjust the CSI-RS density in the frequencydomain. It may also modify the per-resource-block structure of theCSI-RS transmission.

In embodiments, the CSI-RS transmission may be determined based on aper-resource block structure of a CSI-RS resource within a COT. Forexample, a CSI-RS resource associated to the CSI-RS transmissionoccasion may be configured with a CSI-RS resource mapping correspondingto a density of the CSI resource. That is, the transmission occasionconfiguration obtained at 401 may also comprise a CSI-RS resourcemapping corresponding to the density of the CSI resource. The density ofthe CSI resource may be defined as the number (N) of resource elementsper resource block. Based on the outcome of LBT (e.g., duration of theCOT, bandwidth acquired, etc.), the base station may reduce the numberof ports of a given CSI-RS transmission during a COT. For this purpose,the CSI-RS configuration may consist of M aggregated size-x_(i) CSIresources, according to the following Equation 1.

Σ_(i=1) ^(M)x_(i)=N  Eq. 1

Here, M represents the full-sized configured CSI-RS resource by RRC. Thedifferent aggregation level may be indexed from 1 to M.

In embodiment, the density reduction may be explicit. The WTRU receivesin the aperiodic trigger state the density of the CSI resource for theduration of the COT. The WTRU may also receive a DCI with a dedicatedDCI field for the activation of one aggregated level at the start of theCOT.

In embodiment, the density reduction may be implicit, The WTRU may beconfigured with a mapping between aggregation levels and a COT duration.For example, the WTRU may be initially configured with a size-x_(M) CSIresource for COT duration T longer than K slots, that is downsized tosize-_(xM-1) when V≤T<K, and downsized to size-_(xM-2) when W≤T<V etc.This may give aims to the network to prioritize a type of transmission(e.g., PDSCH for high requirements WTRU) over CSI-RS transmission whenthe time duration of the acquired channel is low.

Similarly, the implicit density downsizing may be performed by the WTRUbased on the identification of the acquired sub-bands during the COT. Asimilar mapping between acquired subband and CSI resource density may beconfigured to the WTRU.

In embodiments, the CSI-RS transmission may be determined based on adensity of CSI-RS transmissions. For example, the per-resource-blockstructure outlined above may need to be adapted to the COT start timing.For example, if the COT starts in the middle of a slot, the structuremay be switched to one or more symbols within a given RB where theCSI-RS is transmitted. Thus, the WTRU may maintain the same CSIstructure per resource block (i.e., the same frequency and timeseparation, code division), but only apply a time offset to the start ofCSI-RS transmission within a given RB. The WTRU may either apply thisswitching only to the first slot of the COT or further to multiple slotsof the COT.

In the case of periodic CSI-RS transmission, the WTRU may assume thatthe configured CSI-RS transmission occurs every N^(th) slot.

Similarly, as described above, the WTRU may be configured with a mappingof COT duration and CSI-RS transmission occurrence in time. If the COTduration is greater than K slots, the WTRU may expect a CSI-RStransmission with periodicity of N (for example, every N^(th) slot). Ifthe COT duration is less than K slots, then the WTRU may for exampleexpect a CSI-RS transmission with a periodicity of N-T (that is, everyN-T slot), where T may be a configurable value or may be determined as afunction of K. This modification of time structure can also be signaledby the network by means of a Downlink Control Information (DCI) at theCOT initiation.

In embodiments, the density of CSI-RS transmissions in the frequency maybe modified. For example, the per-resource-block structure outlinedabove may need to be adapted based on the outcome of the base stationchannel acquisition. For example, a CSI-RS may be configured for CSI-RStransmission in every RB corresponding to a density equal to 1, everytwo RBs corresponding to a density equal to ½, etc. The WTRU may furtherbe configured with a relationship between the number of acquiredbandwidth in the active DL Bandwidth Part (BWP) and the density ofCSI-RS transmissions. For example, if all subbands of the active DL BWPare acquired by the base station, the WTRU may expect the lowest densityof CSI-RS transmissions. While if only a subset of the subbands of theactive DL BWP are acquired, the WTRU may expect a higher density of theconfigured CSI-RS within the acquired subbands.

The WTRU may also expect two different density schemes of the CSI-RStransmissions within and outside the COT. If the WTRU has received anindication of a channel acquisition indicating that the base station hasacquired a set of subbands or the WTRU has acquired a set of subbands(i.e., a scenario within the COT), it may apply a first CSI-RStransmission density. If the WTRU or the based station has not acquireda set of subbands (i.e., a scenario outside the COT), the WTRU may applya second density scheme.

The WTRU may be configured with an alternative CSI-RS configuration as asubstitute of the resources associated with the report configuration ofa triggered state that is used by the WTRU only when a set of conditionsare satisfied. These conditions may be associated with at least one ofthe following parameters: COT duration, acquired bandwidth, the numberof previous reported CSI feedback, the number of non-transmitted CSI-RSor the number skipped CSI reports due to LBT failure, etc. It should beappreciated that the above-mentioned parameters associated with theconditions are not intended to be exclusive or be limiting to thepresent application. The conditions may also associated with any otherparameter as long as those conditions may help to realize the principleof the application.

The configured alternative CSI-RS configuration may have, for example, ahigher density in term of time/frequency. For example, the WTRU may beconfigured with a n-port CSI-RS with a given density (e.g., single portCSI-RS with density 3, corresponding to 3 REs per RB). The WTRU mayapply the n-port CSI-RS if the acquired channel bandwidth and/or timeduration is lower than a certain value or if the WTRU has not been ableto perform any measurements on the CSI-RS resources or report feedbackfor the past n timing instances.

In embodiments, the transmission occasion configuration may furthercomprise a CSI-RS triggering offset. The CSI-RS triggering offset mayindicate the number of slots between the slot containing the DCI thattriggers a set of aperiodic non-zero power (NZP) CSI-RS resources andthe slot in which the CSI-RS resource is transmitted.

The CSI-RS resource may have been triggered in a DCI within one COT andtransmitted in a slot of a next COT. If the network has not been able toacquire the channel sufficiently long, the WTRU may consider that theCSI-RS will be transmitted on the minimum value between the COT durationand the CSI-RS triggering offset.

In alternate embodiments, if the CSI-RS transmission slots exceeds themaximum number of slots in the COT duration, the WTRU may monitor theCSI-RS with a dedicated granularity. This granularity may be one of thefollowing: (1) a static preconfigured RRC pattern, e.g., every odd slot;or (2) an RRC pre-configured pattern that is a function of different COTdurations. For example, for COT duration from 1 to x slots, the WTRU maymonitor the CSI with a first granularity (e.g., every slot), for COTduration from x+1 slots to n slots, the WTRU may monitor the CSI with asecond granularity (e.g., every odd or even slot); for COT duration fromn+1 slots to y slots, the WTRU may monitor the CSI with a thirdgranularity (e.g., every t slot), etc. It will be appreciated that theabove examples regarding different granularities are only exemplary, andthey are not intended to be exclusive or be limiting to the presentapplication.

CSI-RS based measurements will be described below. A WTRU operating withmultiple LBT subbands may be configured to perform measurements on oneor multiple CSI-RSs resources present in multiple subbands. In onemethod, the WTRU may expect one or multiple CSI-RSs to be containedwithin a single LBT subband. In such a case, the WTRU may report afeedback for the one or multiple CSI-RSs included in LBT subbands wherethe one or multiple CSI-RSs were transmitted. The WTRU may indicate theset of LBT subbands for which a feedback is reported. In alternateembodiments, the WTRU may pad a feedback report to ensure consistentsize regardless of number of actually transmitted CSI-RS resources.

In an alternate embodiment, a CSI-RS may span multiple LBT subbands. Insuch a case, the WTRU may report measurements for a portion of theCSI-RS that was transmitted. For example, the WTRU may use the subbandreporting such that each subband measurement corresponds to a portion ofthe CSI-RS that was present.

The WTRU may report a wideband CSI feedback covering multiple portionsof the CSI-RS that was present. For example, the WTRU may be configuredwith a CSI-RS spanning a number (x) of LBT subbands. However, the WTRUmay only receive CSI-RS in a first and second LBT subbands. The WTRU maydetermine to report a wideband CSI feedback where the wideband bandwidthis assumed to be the first and second LBT subbands (i.e., all thesubbands where the CSI-RS was received). A wideband feedback may only bedetermined for sets of contiguous LBT subbands. The WTRU may reportmultiple wideband feedbacks, each for sets of contiguous LBT subbands. Awideband CSI feedback may indicate the set of CSI-RS resources (or LBTsubbands) to which the wideband CSI feedback applies.

An embodiment regarding cross COT measurements and reports will bedescribed below. The WTRU may receive a CSI-RS resource in a first COT,but only have applicable feedback resources in a subsequent second COT.In such a case, the WTRU may be configured with a validity timer. TheWTRU may determine the validity of a feedback report based on the timebetween a CSI-RS reception and the next upcoming valid feedback reportresource. In this application, unless otherwise indicated, the terms“feedback” and “feedback report” may be used interchangeably.

In embodiment, a WTRU feeding back measurements in a COT based on CSI-RSresources received in a previous COT may provide measurements applicableto COT parameters or feedback COT parameters. For example, a WTRUreceiving a CSI-RS resource in a first COT composed of a first set ofLBT subbands may only have feedback resources in a second COT composedof a second set of LBT subbands. The WTRU may report at least one of:measurements applicable to the LBT subbands of the first COT,measurements applicable to the LBT subbands of the second COT, ormeasurements applicable to the set of LCT subbands applicable to boththe first and second COT. In such an example, if the CSI-RS received inthe first COT is applicable to the first set of LBT subbands, the secondset of LBT subbands, and the third set of LBT subbands, but the secondCOT is only active in the second set of LBT subbands, then the WTRU mayreport measurements only applicable to the second set of LBT subbands.

A feedback report instance may be tied to a reference slot or asubframe. However, in some cases, the CSI-RS in the reference slot maynot be present. Therefore, the WTRU may assume a set of reference slotsare tied to each feedback report instance.

In one embodiment, the WTRU may only report measurements for a singleCSI-RS occasion within the set of reference slots. The WTRU may use, asa reference slot, the earliest or latest reference slot within the setwhere the CSI-RS is present. In another embodiment, the WTRU may performmeasurements on a subset of reference slots within the set of referenceslots where the CSI-RS is present. In another embodiment, the WTRU mayperform average measurements over a subset of reference slots within theset of reference slots where the CSI-RS is present.

The WTRU may report a feedback even when no CSI-RS was transmitted. Thismay enable AN indication of a hidden note at the WTRU. Such a feedbackmay indicate no valid measurements are available. In another solution,the WTRU may report interference values without desired channelmeasurements applicable to the reference slot (or the set of referenceslots) associated with the CSI-RS resources.

In one embodiment, the WTRU may request a CSI-RS transmission, e.g., ifno CSI-RS is present in the set of reference slots associated with afeedback report occasion. The WTRU's request for the CSI-RS may point toa specific aperiodic/periodic/semi-persistent CSI-RS resource. Forexample, the WTRU's request may come in a WTRU-acquired COT, in whichcase, the WTRU may indicate the parameters of the COT to the network inorder to activate the CSI-RS with COT timing dependencies.

The WTRU may determine the contents of a CSI feedback based on therelative timing of the associated CSI-RS resource and the physicaluplink control channels (PUCCH) or physical uplink shared channels(PUSCH) resource for the CSI feedback. Furthermore, the WTRU maydetermine the contents of a CSI feedback based on parameters associatedwith the CSI-RS transmission and the transmission of the CSI feedback.For example, the WTRU may determine the content of the feedback, andpossibly whether the feedback is to be reported at all, based on whetherthe CSI-RS resource and the CSI feedback resource are in the same COT.For example, if the CSI feedback resource is in the same COT as theassociated CSI-RS resource, the WTRU may provide a full CSI feedbackreport (e.g., including subband reports). If the CSI feedback resourceis in a COT subsequent to the COT where the associated CSI-RS resourceis located, the WTRU may provide a reduced set of CSI reports (e.g.,only wideband values).

In an alternate embodiment, the contents of the CSI feedback report mayalso depend on the time gap between the COT where the CSI-RS resourcewas received and the COT where the CSI feedback is reported. Forexample, as the time gap increases, the WTRU may reduce the granularityof the contents of the feedback report.

In an embodiment, PUCCH resources may be dynamically triggered totransmit CSI feedback. Such dynamically triggered PUCCH resources mayenable the WTRU to perform CAT1 or CAT2 PBT prior to accessing anunlicensed channel.

In an embodiment, the WTRU may be configured with a set of PUCCHresources. The WTRU may only use the set of PUCCH resources if they aredynamically triggered by the base station. The trigger may indicate tothe WTRU a reference slot from which feedback report measurements shouldbe obtained. In another solution, the dynamically triggered PUCCHresources may be preconfigured with a reference slot (or a set ofreference slots) from which to obtain CSI measurements.

CSI feedback may not have value unless a WTRU may be scheduled in theDL. For cases where the WTRU has no valid resources on which to feedbackCSI with a current COT, it may not make sense to acquire a new COT forthe sole purpose of transmitting CSI feedback that may not be useful.The WTRU may (e.g., may only) acquire a COT for the sole purpose oftransmitting CSI feedback if it has been indicated in a previous COTthat it may expect more DL data transmissions. For example, the WTRU mayhave received transmission in a first COT and may have performedmeasurements on a CSI-RS resource present during the first COT. The WTRUmay not have any more feedback resources within the first COT. If theWTRU receives an indication that it may expect more DL datatransmissions in a subsequent COT, the WTRU may attempt to acquire thechannel prior to CSI feedback resources in order to provide the basestation with relevant CSI feedback information.

In an embodiment, the WTRU may acquire the COT and transmit CSI feedbackif it also needs to transmit HARQ feedback for a previous COT. The WTRUmay multiplex the CSI feedback with the HARQ feedback. In a variant ofthe embodiment, the WTRU may only multiplex CSI feedback if there is atleast one Negative Acknowledgement (NACK) in the HARQ feedback, giventhat the WTRU may then expect another DL transmission.

If the WTRU is configured to report multiple CSI feedbacks including aChannel Quality Indicator (CQI), a Channel Resource Indicator (CRI),L1-beam measurement results, Precoding Matrix Indicator (PMI), RankIndicator (RI), Layer Indicator (LI), the WTRU may need to perform LBTto acquire UL resources to transmit the CSI feedback report, and basethe content of the feedback report on the outcome of LBT or timing ofsuccessful LBT. For example, if the WTRU is configured to reportmultiple types of feedback, the WTRU may only report a subset of theconfigured report quantities. The WTRU may be configured with a priorityassociated with the reporting content that is a function of the LBToutcome. For instance, CRI may have the highest priority, CQI thesecond, L1-RSRP the third, PMI the fourth, etc.

The WTRU may also report the quantities associated with one reportinginstance in different reports based on the amount of acquired ULresource or LBT outcome. The WTRU may further indicate to the networkthe association between two different quantities reported in twodifferent reporting instances corresponding to the same trigger state.

A time domain behavior of the CSI-ReportConfig is indicated by a higherlayer parameter reportConfigType and can be set to ‘aperiodic’,‘semiPersistentOnPUCCH’, ‘semiPersistentOnPUSCH’, or ‘periodic’. TheWTRU may have an association of the report configuration type and thetype of LBT where the WTRU may perform to acquire the resources for theCSI feedback. For example, if the WTRU is configured with periodicreporting on PUCCH, it may also be configured with a condition that thePUCCH is only used if it requires an LBT category 2 or lower. Althoughfeatures and elements are described above in particular combinations,one of ordinary skill in the art will appreciate that each feature orelement can be used alone or in any combination with the other featuresand elements. In addition, the methods described herein may beimplemented in a computer program, software, or firmware incorporated ina computer-readable medium for execution by a computer or processor.Examples of computer-readable media include electronic signals(transmitted over wired or wireless connections) and computer-readablestorage media. Examples of computer-readable storage media include, butare not limited to, a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs). A processor in association with software may be used toimplement a radio frequency transceiver for use in a WTRU, UE, terminal,base station, RNC, or any host computer.

It will be appreciated that the terminology used in the presentapplication is for the purpose of describing particular embodiments andis not intended to limit the application. The singular forms “a”, “the”,and “the” may be intended to comprise a plurality of elements. The terms“including” and “comprising” are intended to include a non-exclusiveinclusion. Although the present application is described in detail withreference to the foregoing embodiments, it will be appreciated thatthose foregoing embodiments may be modified, and such modifications donot deviate from the scope of the present application.

1-18. (canceled)
 19. A method for use in a wireless transmit/receiveunit (WTRU), the method comprising: receiving first informationindicating one or more first transmission occasions for receivingchannel state information reference signal (CSI-RS) transmissions;receiving second information indicating one or more second transmissionoccasions for receiving CSI-RS transmissions; and receiving, responsiveto a determination that a CSI-RS transmission is not received in a firstone of the one or more first transmission occasions, a CSI-RStransmission in at least one of the one or more second transmissionoccasions.
 20. The method of claim 19 further comprising: receiving,responsive to a determination that a CSI-RS transmission is received inthe first one of the first set of transmission occasions, for anotherCSI-RS transmission in a second one of the first set of transmissionoccasions.
 21. The method of claim 19, wherein a determination whetherthe first CSI-RS transmission is received in the first one of the firstset of transmission occasions is based on a measurement, based on areceived indication from a base station, or based on a parameter ofanother CSI-RS transmission.
 22. The method of claim 19, wherein thesecond information indicating the one or more second transmissionoccasions for receiving CSI-RS transmissions indicates one or more timeoffset values from one of the one or more first transmission occasions.23. The method of claim 19, wherein at least one parameter of the one ormore first transmission occasions or of the one or more secondtransmission occasions is determined based on a parameter associatedwith a channel occupancy time (COT).
 24. The method of claim 23, whereinthe at least one parameter comprises one or more of: time and frequencyresources, or a number of antenna ports.
 25. The method of claim 19further comprising transmitting information indicative of a feedbackreport, wherein content of the feedback report is based on timing of areceived CSI-RS transmission and timing of the transmission includingthe information indicative of the feedback report.
 26. The method ofclaim 25, wherein the information indicative of the feedback reportprovides feedback associated with a CSI-RS transmission received in aslot, wherein the slot is one of a plurality of slots associated withthe feedback report.
 27. The method of claim 26, wherein the feedbackassociated with the CSI-RS transmission received in the slot comprisesfeedback associated with a plurality of CSI-RS transmissions received ina corresponding plurality of slots.
 28. The method of claim 26, whereinthe feedback report includes one or more of asignal-to-interference-plus-noise ratio (SINR) measurement, a channelquality indicator (CQI), a channel resource indicator (CRI), a precodingmatrix indicator (PMI), a rank indicator, or a layer indicator (LI). 29.A wireless transmit/receive unit (WTRU) comprising: a processor; and atransceiver; the processor and the transceiver configured to receivefirst information indicating one or more first transmission occasionsfor receiving channel state information reference signal (CSI-RS)transmissions; the processor and the transceiver configured to receivesecond information indicating one or more second transmission occasionsfor receiving CSI-RS transmissions; and the processor and thetransceiver configured to receive, responsive to a determination that aCSI-RS transmission is not received in a first one of the one or morefirst transmission occasions, a CSI-RS transmission in at least one ofthe one or more second transmission occasions.
 30. The WTRU of claim 29,wherein the processor and the transceiver are configured to receive,responsive to a determination that a CSI-RS transmission is received inthe first one of the first set of transmission occasions, for anotherCSI-RS transmission in a second one of the first set of transmissionoccasions.
 31. The WTRU of claim 29, wherein a determination whether thefirst CSI-RS transmission is received in the first one of the first setof transmission occasions is based on a measurement, based on a receivedindication from a base station, or based on a parameter of anotherCSI-RS transmission.
 32. The WTRU of claim 29, wherein the secondinformation indicating the one or more second transmission occasions forreceiving CSI-RS transmissions indicates one or more time offset valuesfrom one of the one or more first transmission occasions.
 33. The WTRUof claim 29, wherein at least one parameter of the one or more firsttransmission occasions or of the one or more second transmissionoccasions is determined based on a parameter associated with a channeloccupancy time (COT).
 34. The WTRU of claim 33, wherein the at least oneparameter comprises one or more of: time and frequency resources, or anumber of antenna ports.
 35. The WTRU of claim 29 wherein the processorand the transceiver are configured to transmit information indicative ofa feedback report, wherein content of the feedback report is based ontiming of a received CSI-RS transmission and timing of the transmissionincluding the information indicative of the feedback report.
 36. TheWTRU of claim 35, wherein the information indicative of the feedbackreport provides feedback associated with a CSI-RS transmission receivedin a slot, wherein the slot is one of a plurality of slots associatedwith the feedback report.
 37. The WTRU of claim 36, wherein the feedbackassociated with the CSI-RS transmission received in the slot comprisesfeedback associated with a plurality of CSI-RS transmissions received ina corresponding plurality of slots.
 38. The WTRU of claim 36, whereinthe feedback report includes one or more of asignal-to-interference-plus-noise ratio (SINR) measurement, a channelquality indicator (CQI), a channel resource indicator (CRI), a precodingmatrix indicator (PMI), a rank indicator, or a layer indicator (LI).